1. Field of the Invention
The present invention relates to the treatment of contaminated water. More particularly, the present invention relates to the treatment of contaminated water through the use of membrane biological reactors. Additionally, the present invention relates to a process for treating contaminated water whereby the growth of phototrophic organisms is used to remove the nitrogen and phosphorus content from the contaminated water.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98
Contaminated water is often treated through a wide variety of processes. Often, the contaminated water is filtered and treated so that a suitable treated water is passed from the treatment system. Unfortunately, the treated water often has a very high nitrogen and phosphorus content. As such, it is necessary to employ additional systems in a relatively costly and inefficient manner so as to remove such nitrogen and phosphorus content from the treated water.
Membrane biological reactors are known in the past. The membrane biological reactor is a combination of a membrane process, such as microfiltration or ultrafiltration, along with a suspended growth bioreactor. Such membrane biological reactors are widely used in municipal and industrial wastewater treatment. When used with domestic wastewater treatment, membrane biological reactor processes produce an effluent of a high quality suitable for being discharged to coastal, surface or brackish waterways or to be reclaimed for urban irrigation. Other advantages of membrane biological reactors over conventional processes include a small footprint, an easy retrofit and an upgradability of old wastewater treatment plants. It is possible to operate membrane biological reactor processes at higher mixed liquor suspended solids concentrations compared to conventional settlement separation systems. This reduces the reactor volume to achieve the same loading rate.
Two types of membrane biological reactor configurations exist. These are the internal/submerged systems and the external/sidestream systems. In the internal/submerged systems, the membranes are immersed in and integral to the biological reactor. In the external/sidestream systems, the membranes are a separate unit process requiring an intermediate pumping step.
Recent technical innovations and significant membrane cost reductions have pushed membrane biological reactors to become an established process option to treat wastewaters. As a result, the membrane biological reactor process has now become an attractive option for the treatment and reuse of industrial and municipal wastewaters, as evidenced by their constantly rising numbers and capacities.
Unfortunately, such membrane biological reactors are unable to significantly reduce the nitrogen and phosphorus content of the filtrate of the system. As such, additional steps are necessary so as to remove the nitrogen and phosphorus content to a level suitable for making the filtered water output of a suitably potable nature.
Algae fuel is a biofuel which is derived from algae. During photosynthesis, algae and other synthetic organisms capture carbon dioxide and sunlight and convert it into oxygen and biomass. Up to 99% of the carbon dioxide in solution can be converted in large scale open-pond systems. Several companies and government agencies are funding efforts to reduce capital and operating costs and make algae oil production commercially viable. The production of biofuels from algae does not reduce atmospheric carbon dioxide, because any carbon dioxide taken out the atmosphere by the algae is returned when the biofuels are burned. They do eliminate the introduction of new carbon dioxide by displacing fossil carbon fuels.
High oil prices and competing demands between foods and other biofuel sources and the world food crisis have ignited interest in algaculture (farming algae) so as to make vegetable oil, biodesiel, bioethanol, biogasoline, biomethanol, biobutanol and other biofuels by using land that is not suitable for agriculture. Among algal fuel's attractive characteristics is that it does not affect fresh water resources, can be produced using ocean and wastewater, and is biodegradable and relatively harmless to the environment if spilled. Algae can yield over thirty times more energy per unit area than other second-generation biofuel crops. The United States Department of Energy estimates that if algae replaced all petroleum fuel in the United States, it would require 15,000 square miles of land. This is less than one-seventh of the area of corn harvested in the United States.
Algae can produce up to 300 times more oil per acre than conventional crops, such as rapeseed, palms or soy beans. Since algae has a harvesting cycle of between one and ten days, it permits several harvests in a very short time period. Algae can be grown on land that is not suitable for other crops. This minimizes the issue of taking any pieces of land from the cultivation of food crops.
Most companies that are pursuing algae as a source of biofuels are pumping nutrient-laden waters through plastic tubes that are exposed to sunlight. Generally, the use of a photobioreactor is more difficult than an open pond and more costly. Another obstacle preventing widespread mass production of algae for biofuel production has been the equipment and structures needed to begin growing algae in large quantities. In closed loop systems, there is no problem of contamination by other organisms blown in by the air.
Algal market models indicate the development of fuels from algae will follow the pattern of crude oil from specialty to commodity chemical models of the 1920's and 1930's. The distinct difference is that during this period of time, the markets were required to be created, whereas today, the markets already exist.
Although “algal oil to transportation fuels” has been the driving force to date, only the co-products of algae oil production will bring economic stability to the market. As in the oil refining business, transportation fuel production alone is incapable of supporting the current cost of producing fuels due to the imbalance in supply and demand.
Each pound of algae produces about 0.4 pounds of algae protein meal, 0.2 pounds of carbohydrates, and 0.3 pounds of algae oil. Algae meal can be a major protein supplement used in aquatic, livestock and poultry feeds. As such, herd and flock numbers are major influences on algae meal consumption and prices. Algae products are and will be used to manufacture fuels, fuel feedstocks, foodstuffs, food products, and ethanol. Technical uses include adhesives, cleansing materials, polyesters, inks, coatings, polymers, detergents, quaternary salts, pharmaceuticals, chemical and biological feedstocks and other textiles.
The current demand for algal products is severely outpaced by the supply. It is not anticipated that supply will be capable of meeting demand for at least 15-20 years. Therefore, algal products will follow the classical specialty chemical models from current to at least ten years out. The transition from specialty to commodity will occur after that, first being noticed by variable market pricing swings from high to low.
As long as the demand outpaces supply, algal producers will continually pursue the “highest value” markets. These markets will consist of pharmaceuticals, plastics, nutraceuticals and specialty chemical feedstocks. As supply and demand come into balance, algal products will begin leaking over into the commodity models. Only then will the algal products be used in the transportation fuel markets. Once algae biomass becomes a commodity in the market, futures and options markets will develop. As such, there is a need for utilizing algae production so as to maximize the fuel output and to utilize the various components of the algae in an optimal and efficient manner.
In the past, various patents have been issued in the field of microorganisms growth and relating to processing bio-harvests. For example, U.S. Pat. No. 6,599,735, issued on Jul. 29, 2003 to Bartok et al., describes a fermentation assembly comprising a vessel for culturing living cells, at least two storage flasks in fluid communication with the vessel for supply of liquids and a first transport means for transferring the liquids from the storage flasks to the vessel, individual appliances operably connected to the transport means for monitoring the supply of the contents of the storage flasks to the vessel, a harvest flask in fluid communication with the vessel and a second transport means for transferring the fermentation broth from the vessel to the harvest flask, and a device operably connected to the first transport means for controlling and maintaining a constant dilution rate in the vessel with varying rates of individual supply of liquid from the storage flasks to the vessel.
U.S. Pat. No. 5,688,674, issued on Nov. 18, 1997 to Choi et al., describes a metabolite, e.g., ethanol, that is continuously produced from low cost carbohydrate substrates by a process which comprises pulverizing the carbohydrate substrate, liquefying and saccharifying the pulverized substrate, continuously fermenting the lique-saccharified substrate in a fermentor equipped with a moving filter, in the presence of flocculent biological cells maintained at a concentration ranging from 90 to 160 grams/liter by using the moving filter and a culture medium to produce a fermentation product mixture, and recovering the desired metabolite from the fermentation product mixture.
U.S. Pat. No. 4,069,149, issued on Jan. 17, 1978 to Jackson, describes a deep-tank reactor utilized for fermentation of waste liquid or other liquid in a biological reaction resulting in a solid cellular material. The resulting solid material, which is in suspension, is initially separated from the bulk of the liquid by a gaseous flotation process, using the dissolved gas in the liquid as the source of gaseous bubbles for flotation purposes.
U.S. Pat. No. 4,286,066, issued on Aug. 25, 1981 to Butler et al., describes an apparatus for continuously fermenting a moist particulate feed and distilling the fermentation product where a pressure-locked auger forces a moist particulate feed from a hopper into a fermentation tank. Liquor is removed from the tank, and solids are separated therefrom, to produce a beer which is distilled in a distillation column. A combustion engine powers the auger and the means for separating solids, and the engine exhaust surrounds an inlet section of said auger to help heat the pressurized feed therein to produce fermentable sugar within the auger. The auger includes a section passing to the tank in beat exchange relation to the distillation column to provide heat for distillation. The column is a multistage column angled to face the sun and has an upper glass plate to allow solar radiation to enter and penetrate between the foraminous plates of the column.
It is an object of the present invention to provide a process whereby contaminated water can be effectively treated so as to remove COD, BOD, TSS, along with nitrogen and phosphorus.
It is still another object of the present invention to provide a process whereby the filtrate from the membrane biological reactors can be utilized for supplying nitrogen and oxygen to a High Rate Algal Growth system (HRAG).
It is still a further object of the present invention to provide a system for the treatment of contaminated water whereby the output of the process is potable water.
It is still another object of the present invention to provide a system for the treatment of contaminated water which utilizes both continuous stirred tank reactors and plug flow reactors.
It is still a further object of the present invention to provide a process for the treatment of contaminated water that achieves a growth rate of algae exceeding 120 grams/m2/day.
It is still a further object of the present invention to provide a process for the treatment of contaminated water that optimizes light energy usage.
It is still a further object of the present invention to provide a system for the treatment of contaminated water which optimizes the growth of algae through a combination of “light” and “dark” reactions in a commercially scalable configuration.
It is still a further object of the present invention to provide a process for the treatment of contaminated water that maximizes and controls the usage of carbon dioxide as a feedstock for the reaction.
It is still another object of the present invention to provide a process for the treatment of contaminated water that minimizes the footprint required for the treatment process.
These and other objects and advantages of the present invention will become apparent from a reading of the attached specification and appended claims.